The fire detector technology has developed different systems, utilizing ionization chambers, optical arrangements, and gas sensors, for detecting the presence of particles of combustion when a fire is still in the incipient stages. Regardless of the particular sensor used, the system must have an effective housing to admit the gases with entrained particles of combustion so that the detector can operate to recognize presence of the particles. In ionization type detectors, a minute electrical current developed between two collector plates is diminished when the smoke particles enter the ionized space and impede passage of the ions. The detector can be "fooled" and provide a spurious fire signal if a gust of wind passes through the chamber and blows out the ions, diminishing the current flow to a degree which simulates the reduced current flow caused by entrance of particles of combustion. Accordingly considerable effort has been directed to providing the best possible entry of gases with the entrained particles, while attempting to minimize the possibility of too-rapid or straight-line passage through the detector to remove the ions and cause an inaccurate fire signal. Even with these considerable efforts there is substantial room for improvement in the housing characteristics.
It is therefore a primary object of the present invention to provide a smoke detector housing which has an effective "window" or particle entrance area substantially larger than those of earlier housings.
Another important object of the invention is to provide such a housing which precludes the direct-line passage of particles through the detector housing.
Yet another important object of the present invention is to provide a smoke detector housing which readily admits particles but retards their egress, to effect a rapid virtual equality of the particle density within the housing and the particle density external to the housing, to produce early detection of the fire.